info
Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
JS3 real world performance
2,091 views
Skip to first unread message
Andrew Herwig
Nov 17, 2021, 6:50:30 PM11/17/21
to
A lot has been said about the performance of the JS3 and how it compares to previous generation gliders such as the ASG29, Ventus 2CX etc. However has anyone actually flown alongside this ship in a 29 or 2cx for a good period of time to determine how much better it is. I ask because looking at the polars the JS3 at 100k = 1.2m/s sink rate vs the Ventus 2CX at 1.5m/s sink rate. This is 20% better than the Ventus and translates to about about a 600 foot difference in a 10 minute glide at 100 knots which to me seems a huge difference. This 600 ft height difference is going to take about 2 minutes to make up in in a 3 knot climb! A 20% difference in time! Given the typical cross country "cruise" component is about 70% of the total task time this is still a 14% overall difference. A very significant amount.
I note however that the DMSt handicap for the JS3, Ventus 2CXA and the ASG29 is actually the same at 119. Even in Australia the handicap difference is only about 1.4%. I understand the reality of the faster gliders pulling the slower gliders along in a competition however 14% is still a huge difference. Are the polars for the newer gliders exaggerated or are they really that much better in reality.
Andrew
I note however that the DMSt handicap for the JS3, Ventus 2CXA and the ASG29 is actually the same at 119. Even in Australia the handicap difference is only about 1.4%. I understand the reality of the faster gliders pulling the slower gliders along in a competition however 14% is still a huge difference. Are the polars for the newer gliders exaggerated or are they really that much better in reality.
Andrew
Jeffrey Resnik
Nov 17, 2021, 7:24:45 PM11/17/21
to
Have you viewed the comprehensive analysis prepared and displayed in this video by Clemens?
https://www.youtube.com/watch?v=Tj2sv6eQRTU&t=68s
https://www.youtube.com/watch?v=Tj2sv6eQRTU&t=68s
Steve Koerner
Nov 17, 2021, 11:00:03 PM11/17/21
to
For what it's worth Idaflieg conducted side by side testing of the JS3 against their holy cow glider in 2020. I haven't personally read the report but according to the Jan 2021 JS Newsletter, Idafleg determined that the JS3 achieved 57:1 in their testing. That's just one point on the curve, but an impressive point it is.
Komisia bezmotorového lietania Sna
Nov 18, 2021, 8:35:11 AM11/18/21
to
haven't got personal experience - just heard a lot of pub talk about it. However Czech index list (which I consider very fine tuned) gives these gliders these handicaps (18m, with water ballast):
Ventus 2cx 120.2
Ventus 2cxa. 120.5
ASG29. 121.3
JS3. 122.7
just my 2 cents..
Dňa štvrtok 18. novembra 2021 o 0:50:30 UTC+1 používateľ Andrew Herwig napísal:
Ventus 2cx 120.2
Ventus 2cxa. 120.5
ASG29. 121.3
JS3. 122.7
just my 2 cents..
Dňa štvrtok 18. novembra 2021 o 0:50:30 UTC+1 používateľ Andrew Herwig napísal:
John Galloway
Nov 18, 2021, 12:10:04 PM11/18/21
to
Eric Greenwell
Nov 18, 2021, 1:53:38 PM11/18/21
to
On 11/17/2021 3:50 PM, Andrew Herwig wrote:
> A lot has been said about the performance of the JS3 and how it compares to previous generation gliders such as the ASG29, Ventus 2CX etc. However has anyone actually flown alongside this ship in a 29 or 2cx for a good period of time to determine how much better it is. I ask because looking at the polars the JS3 at 100k = 1.2m/s sink rate vs the Ventus 2CX at 1.5m/s sink rate. This is 20% better than the Ventus and translates to about about a 600 foot difference in a 10 minute glide at 100 knots which to me seems a huge difference. This 600 ft height difference is going to take about 2 minutes to make up in in a 3 knot climb! A 20% difference in time! Given the typical cross country "cruise" component is about 70% of the total task time this is still a 14% overall difference. A very significant amount.
>
> I note however that the DMSt handicap for the JS3, Ventus 2CXA and the ASG29 is actually the same at 119. Even in Australia the handicap difference is only about 1.4%. I understand the reality of the faster gliders pulling the slower gliders along in a competition however 14% is still a huge difference. Are the polars for the newer gliders exaggerated or are they really that much better in reality.
Perhaps it is your comparison that is awry; for example, was the wing loading the same for
> A lot has been said about the performance of the JS3 and how it compares to previous generation gliders such as the ASG29, Ventus 2CX etc. However has anyone actually flown alongside this ship in a 29 or 2cx for a good period of time to determine how much better it is. I ask because looking at the polars the JS3 at 100k = 1.2m/s sink rate vs the Ventus 2CX at 1.5m/s sink rate. This is 20% better than the Ventus and translates to about about a 600 foot difference in a 10 minute glide at 100 knots which to me seems a huge difference. This 600 ft height difference is going to take about 2 minutes to make up in in a 3 knot climb! A 20% difference in time! Given the typical cross country "cruise" component is about 70% of the total task time this is still a 14% overall difference. A very significant amount.
>
> I note however that the DMSt handicap for the JS3, Ventus 2CXA and the ASG29 is actually the same at 119. Even in Australia the handicap difference is only about 1.4%. I understand the reality of the faster gliders pulling the slower gliders along in a competition however 14% is still a huge difference. Are the polars for the newer gliders exaggerated or are they really that much better in reality.
both polars? Also, 100kph is very slow, more like thermalling speed, not cruise speed when
thermals are 3 knots.
--
Eric Greenwell - USA
- "A Guide to Self-launching Sailplane Operation"
https://sites.google.com/site/motorgliders/publications/download-the-guide-1
R
Nov 18, 2021, 5:42:22 PM11/18/21
to
On Thursday, November 18, 2021 at 1:53:38 PM UTC-5, Eric Greenwell wrote:
> On 11/17/2021 3:50 PM, Andrew .
R
> On 11/17/2021 3:50 PM, Andrew .
> Perhaps it is your comparison that is awry; for example, was the wing loading the same for
> both polars? Also, 100kph is very slow, more like thermalling speed, not cruise speed when
> thermals are 3 knots.
>
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
I'm reading knots in the ops opening.
> both polars? Also, 100kph is very slow, more like thermalling speed, not cruise speed when
> thermals are 3 knots.
>
> --
> Eric Greenwell - USA
> - "A Guide to Self-launching Sailplane Operation"
> https://sites.google.com/site/motorgliders/publications/download-the-guide-1
R
youngbl...@gmail.com
Nov 18, 2021, 6:00:38 PM11/18/21
to
Eric Greenwell
Nov 18, 2021, 6:24:02 PM11/18/21
to
since "k" usually means kilometers, and 100 knots is a high speed for 3 knot thermals. I'm
sticking with "awry comparison" until there are more details
2G
Nov 18, 2021, 7:55:31 PM11/18/21
to
Andrew Herwig
Nov 18, 2021, 9:55:49 PM11/18/21
to
From feedback and comments(unfortunately not from actual flight comparisons as requested) I am still convinced there is a large performance difference which is not reflected in the handicaps. A JS3 can do 100 knots with an l/d of 40. That is twice the speed at the best l/d of older gliders yet the handicap difference here in Australia between that an a std Jantar is only about 12%
I did look at Clemens report JS3 vs Ventus 2ct and also had a quick look at the video. Thanks for the link. The report suggests that there is not a whole lot in it but the video suggests to me there is a larger difference when the flight was analysed. 170 vs 190 km/hr is a big difference particularly given Seaborn flew too fast and wasted energy. Great report and really good video. I'll keep the video in mind for coaching purposes as it demonstrates well how to fly fast.
Still waiting to hear from anyone who has flown close to a JS3 in a generation older 18m.
Regards Andrew
Eric Greenwell
Nov 18, 2021, 11:24:54 PM11/18/21
to
may be enough to explain most of the difference you saw when comparing polars. Do the
polar diagrams show the wing loadings for the gliders?
Matthew Scutter
Nov 18, 2021, 11:33:44 PM11/18/21
to
Arbitrary points on the polar don't matter that much - XC speed matters. You can approximately calculate that via Macready theory with an estimated climb rate. You can read a more complete approach in papers like Prof. Kubrynski's papers - http://www.dianasailplanes.com/Tech_Soar_KK.pdf
I don't think you'll ever find a sensible handicapping system that works for the range of Jantar to JS3. Handicaps really only 'work' within a small range of similar span and wingloading-range gliders, anything else increases the lottery / weather factor such to the point it's much less fun (in my opinion).
Trying to composite facts about minute differences in glider performance from anecdotes of pilots of differing abilities on differing routes in a dynamic sky is a folly, you're trying to extract a tiny signal from an extremely noisy environment. I do not envy those who sit on handicap committees.
I don't think you'll ever find a sensible handicapping system that works for the range of Jantar to JS3. Handicaps really only 'work' within a small range of similar span and wingloading-range gliders, anything else increases the lottery / weather factor such to the point it's much less fun (in my opinion).
Trying to composite facts about minute differences in glider performance from anecdotes of pilots of differing abilities on differing routes in a dynamic sky is a folly, you're trying to extract a tiny signal from an extremely noisy environment. I do not envy those who sit on handicap committees.
Tim Taylor
Nov 19, 2021, 12:51:10 AM11/19/21
to
Most of the JS3 advantage is the abilty to carry a higher wingloading on very strong days. If the day is very strong with good streeting a fully loaded JS3 has an advantage. They do well in Western US and SA conditions during the peak of the season.
Overall the three current generation gliders are very similar and have advantages and disadvantage based on the weather. The ASG-29 is still very close and actually won the contest this year. The Ventus 2cxa is still a strong contender if conditions are weaker or flights are in the early or later part of the day.
There is no glider that is better then the others in all condtions. Each was designed for slightly different missions and comes with different handling and feel. Pick the one that fits your mission and flying style.
Eric Greenwell
Nov 19, 2021, 11:57:10 AM11/19/21
to
On 11/18/2021 9:51 PM, Tim Taylor wrote:
>>
>> From feedback and comments(unfortunately not from actual flight comparisons as requested) I am still convinced there is a large performance difference which is not reflected in the handicaps. A JS3 can do 100 knots with an l/d of 40. That is twice the speed at the best l/d of older gliders yet the handicap difference here in Australia between that an a std Jantar is only about 12%
>>
>> I did look at Clemens report JS3 vs Ventus 2ct and also had a quick look at the video. Thanks for the link. The report suggests that there is not a whole lot in it but the video suggests to me there is a larger difference when the flight was analysed. 170 vs 190 km/hr is a big difference particularly given Seaborn flew too fast and wasted energy. Great report and really good video. I'll keep the video in mind for coaching purposes as it demonstrates well how to fly fast.
>>
>> Still waiting to hear from anyone who has flown close to a JS3 in a generation older 18m.
>>
>> Regards Andrew
>
> I think drawing concluions from N=1 day and not including the differences in pilot skill would be a mistake. On the day in question I beat the Ventus 2ct by 5 kph flying a 15M Ventus 2a. Is my 15m Ventus 2a 2.5% better than an 18m Ventus 2ct?
>
> Most of the JS3 advantage is the abilty to carry a higher wingloading on very strong days. If the day is very strong with good streeting a fully loaded JS3 has an advantage. They do well in Western US and SA conditions during the peak of the season.
>
> Overall the three current generation gliders are very similar and have advantages and disadvantage based on the weather. The ASG-29 is still very close and actually won the contest this year. The Ventus 2cxa is still a strong contender if conditions are weaker or flights are in the early or later part of the day.
>
> There is no glider that is better then the others in all condtions. Each was designed for slightly different missions and comes with different handling and feel. Pick the one that fits your mission and flying style.
A good example of Tim's remarks was the 15M Class at the IGC World championship this year,
>>
>> From feedback and comments(unfortunately not from actual flight comparisons as requested) I am still convinced there is a large performance difference which is not reflected in the handicaps. A JS3 can do 100 knots with an l/d of 40. That is twice the speed at the best l/d of older gliders yet the handicap difference here in Australia between that an a std Jantar is only about 12%
>>
>> I did look at Clemens report JS3 vs Ventus 2ct and also had a quick look at the video. Thanks for the link. The report suggests that there is not a whole lot in it but the video suggests to me there is a larger difference when the flight was analysed. 170 vs 190 km/hr is a big difference particularly given Seaborn flew too fast and wasted energy. Great report and really good video. I'll keep the video in mind for coaching purposes as it demonstrates well how to fly fast.
>>
>> Still waiting to hear from anyone who has flown close to a JS3 in a generation older 18m.
>>
>> Regards Andrew
>
> I think drawing concluions from N=1 day and not including the differences in pilot skill would be a mistake. On the day in question I beat the Ventus 2ct by 5 kph flying a 15M Ventus 2a. Is my 15m Ventus 2a 2.5% better than an 18m Ventus 2ct?
>
> Most of the JS3 advantage is the abilty to carry a higher wingloading on very strong days. If the day is very strong with good streeting a fully loaded JS3 has an advantage. They do well in Western US and SA conditions during the peak of the season.
>
> Overall the three current generation gliders are very similar and have advantages and disadvantage based on the weather. The ASG-29 is still very close and actually won the contest this year. The Ventus 2cxa is still a strong contender if conditions are weaker or flights are in the early or later part of the day.
>
> There is no glider that is better then the others in all condtions. Each was designed for slightly different missions and comes with different handling and feel. Pick the one that fits your mission and flying style.
which had Diana 2 gliders in the top 3 places, despite having only 4 gliders in the
contest, compared to 16 of the JS3 gliders. Is the Diana a super glider? Maybe it was in
those very weak conditions, with it's 28 kg/m2 minimum wing loading versus the 40 kg/m2 of
the JS3 (both numbers from the respective factory websites). Wing loading matters at both
ends of the scale, but it's very difficult to be the best at both ends, so do as Tim says:
"Pick the one that fits your mission and flying style."
"Pick the one that fits your mission and flying style."
marginal final glide
Nov 19, 2021, 2:37:10 PM11/19/21
to
or your wallet.. :D
Dňa piatok 19. novembra 2021 o 17:57:10 UTC+1 používateľ Eric Greenwell napísal:
Dňa piatok 19. novembra 2021 o 17:57:10 UTC+1 používateľ Eric Greenwell napísal:
Jim Lee
Nov 20, 2021, 6:29:35 PM11/20/21
to
Marginal Final Glide, where can I find the handicap list from the Czechs that you mention?
Appreciate the comments from Tim and Matthew.
I did a little study following the Hobbs 18m/Open Nationals. The 18meters and the Opens flew the same course with the same start times each day. In other words, we flew together every day of the contest. I took the 18m day winners speed, which was the JS3, ASG-29, and others. Added up the total speed divided by the number of days to get the average winners' speed for the contest. Did the same thing with the top JS1-21m speed of the day, to arrive at the average fastest JS1 speed for the contest. I felt that I could easily have my way with the 18 meters. Arrive at the top of the gaggles after a glide, sit on top of the gaggle, or lead out first on top of the gaggle. In other words, the performance advantage of 21 meters of wingspan vs 18 meters of wingspan was very noticeable.
So what does "very noticeable" to the observer pan out to be in numbers? .6%. That is point six percent, lets call it half a percent. Not even one percent! Having 3 meters of additional wingspan amongst modern gliders comes out to very little real world performance difference over the course of several competition days. But you can see the difference.
So how much difference in same-span gliders do you think we are likely to see? I get a nice chuckle when I read about hundreds of feet of difference after a short glide comparison between the "old" models vs the "new" models. 20% and such is just not there. But from my experience, it doesn't take much performance increase to realize real performance advantages when racing. I believe that the JS3-18 goes better than my JS1-18 from quite a bit of time in both gliders, and racing in both gliders, including the recent Nephi 18m Nationals. I ascribe this to the improved fuselage streamlining, higher wing aspect ratio, higher wingloading, and most importantly, the additional six inches of span due to the high wing location of the JS3. So how much difference in numbers? I'm sure it's not half a percent, but you can see the difference.
Appreciate the comments from Tim and Matthew.
I did a little study following the Hobbs 18m/Open Nationals. The 18meters and the Opens flew the same course with the same start times each day. In other words, we flew together every day of the contest. I took the 18m day winners speed, which was the JS3, ASG-29, and others. Added up the total speed divided by the number of days to get the average winners' speed for the contest. Did the same thing with the top JS1-21m speed of the day, to arrive at the average fastest JS1 speed for the contest. I felt that I could easily have my way with the 18 meters. Arrive at the top of the gaggles after a glide, sit on top of the gaggle, or lead out first on top of the gaggle. In other words, the performance advantage of 21 meters of wingspan vs 18 meters of wingspan was very noticeable.
So what does "very noticeable" to the observer pan out to be in numbers? .6%. That is point six percent, lets call it half a percent. Not even one percent! Having 3 meters of additional wingspan amongst modern gliders comes out to very little real world performance difference over the course of several competition days. But you can see the difference.
So how much difference in same-span gliders do you think we are likely to see? I get a nice chuckle when I read about hundreds of feet of difference after a short glide comparison between the "old" models vs the "new" models. 20% and such is just not there. But from my experience, it doesn't take much performance increase to realize real performance advantages when racing. I believe that the JS3-18 goes better than my JS1-18 from quite a bit of time in both gliders, and racing in both gliders, including the recent Nephi 18m Nationals. I ascribe this to the improved fuselage streamlining, higher wing aspect ratio, higher wingloading, and most importantly, the additional six inches of span due to the high wing location of the JS3. So how much difference in numbers? I'm sure it's not half a percent, but you can see the difference.
Andrew Herwig
Nov 21, 2021, 5:42:35 AM11/21/21
to
thanks for your comments and observations. I think you have confirmed to me why the handicaps between gliders of a relatively similar performance are what they are. That is the handicaps do not truly represent the actual performance difference between gliders but represent the difference in a competition environment. That is where the higher performing gliders pull the lower performing gliders along.
It is very interesting what you say about the 20% difference in glide ratio not actually being there. That is what I have been trying to determine in whether the published polars are realistic. Yes I agree that any slight performance gain in a high level competition can not be ignored and is the reason why the new generation gliders will just about always be on the podium.
regards
Andrew
Andrew Herwig
Nov 21, 2021, 5:50:10 AM11/21/21
to
Hi Matthew,
I totally agree about handicap dificulties between large glider performance. Unfortunately we live with this all the time in our current environment and it will never be truly fair in all conditions. Yes trying to get answers on an Anecdotal basis is a bit fruitless which is why I was interested in a real world side by side comparison. I think I will have to organise one myself at our club when I can get Lumpy to participate.
regards
Andrew
GCWA
I totally agree about handicap dificulties between large glider performance. Unfortunately we live with this all the time in our current environment and it will never be truly fair in all conditions. Yes trying to get answers on an Anecdotal basis is a bit fruitless which is why I was interested in a real world side by side comparison. I think I will have to organise one myself at our club when I can get Lumpy to participate.
regards
Andrew
GCWA
Matthew Scutter
Nov 21, 2021, 6:27:43 AM11/21/21
to
I think you missed my point - a real-world side-by-side comparison won't give you much to handicap on. Perhaps you will be able to determine the better glider, but the signal is so weak and the noise is so high that without specialist equipment you'll just have another anecdote, not something you can set a handicap from.
Chris Wedgwood
Nov 21, 2021, 6:38:40 AM11/21/21
to
Here's a description of how they calculate the DMsT list. It's in German, but google transalte will do a reasonable job.
https://magazine.weglide.org/indexliste-2022/
https://magazine.weglide.org/indexliste-2022/
Dan Daly
Nov 21, 2021, 7:37:57 AM11/21/21
to
On Sunday, November 21, 2021 at 6:38:40 AM UTC-5, oxo.c...@gmail.com wrote:
> Here's a description of how they calculate the DMsT list. It's in German, but google transalte will do a reasonable job.
>
> https://magazine.weglide.org/indexliste-2022/
Interesting reading; I assume the OLC indexes will change to reflect the DMSt list, and that Condor will also change at some point in the future (when it's ready of course)? Thanks for the link!
> Here's a description of how they calculate the DMsT list. It's in German, but google transalte will do a reasonable job.
>
> https://magazine.weglide.org/indexliste-2022/
Message has been deleted
marginal final glide
Nov 22, 2021, 2:52:38 AM11/22/21
to
Jim Lee - link for download (latest version) is is here: http://www.lkka.cz/sport/docs/CZIL.xls
it is in czech language, but should be obvious - there are two tabs "s vodou" - means with water ballast, and "Bez vody" (without water ballast).. Without water ballast is used for club class comps, with water for so called combined classes of (std, 15m, 18m and open class) gliders.
third tab (called "CPS") is used for scoring of decentralised competition - similar to German DMST/OLC
if any further questions about it, just give me shout.. pleased to help
MFG
Dňa nedeľa 21. novembra 2021 o 0:29:35 UTC+1 používateľ Jim Lee napísal:
it is in czech language, but should be obvious - there are two tabs "s vodou" - means with water ballast, and "Bez vody" (without water ballast).. Without water ballast is used for club class comps, with water for so called combined classes of (std, 15m, 18m and open class) gliders.
third tab (called "CPS") is used for scoring of decentralised competition - similar to German DMST/OLC
if any further questions about it, just give me shout.. pleased to help
MFG
Dňa nedeľa 21. novembra 2021 o 0:29:35 UTC+1 používateľ Jim Lee napísal:
Jim Lee
Nov 22, 2021, 11:06:50 AM11/22/21
to
Thank you MFG!
Jon May
Nov 22, 2021, 4:06:12 PM11/22/21
to
On Monday, 22 November 2021 at 16:06:50 UTC, Jim Lee wrote:
> //www.weglide.org/flight/113169
This gives some idea of how good A JS3 is when the conditions are strong.
Jon
> //www.weglide.org/flight/113169
This gives some idea of how good A JS3 is when the conditions are strong.
Jon
0 new messages